The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various methods and structures to form synchronous rectifiers. One example of a synchronous rectifier was disclosed in U.S. Pat. No. 6,271,712 issued Alan Ball on Aug. 7, 2001, which is hereby incorporated herein by reference. As shown in the Alan Ball patent, the prior synchronous rectifier typically included a comparator that drove a power metal oxide semiconductor field effect transistor (MOSFET). One input of the comparator was coupled to the drain of the MOSFET in order to sense the source-to-drain voltage of the MOSFET, and to enable the MOSFET when the drain voltage was less than a source voltage value that would turn on a parasitic diode of the MOSFET. When enabled, the MOSFET discharged current from an inductor through the MOSFET. However, in order to turn-off the MOSFET, the source-to-drain voltage had to be greater than zero volts. This resulted in both the upper transistor and the synchronous rectifier being simultaneously enabled and increased the power dissipation of the synchronous rectifier. Additionally, because the comparator input was coupled to the drain of the MOSFET, the maximum voltage that could be applied to the drain was limited by the breakdown voltage of the input of the comparator.
Accordingly, it is desirable to have a device that turns off when the source-to-drain voltage is no greater than zero volts, and that has a high breakdown voltage.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention.